1. Field of the Invention
The present invention relates to improvements in tramper's packs.
2. Description of the Prior Art
A tramper's pack comprises a sac in which equipment may be carried, the sac being unframed or mounted on an external or internal frame, and a shoulder harness secured to the sac by means of which the sac is supported on the wearer's back. Carrying a heavy load supported only from the shoulders can lead to backache or even to back damage, so many modern packs include a hip-belt connected at or close to the base of the sac, to transfer some of the load from the shoulders to the hips. However, although using a hip-belt alleviates the loading on the back, the hip-belt itself causes problems to the wearer, due to the way in which the human body moves when walking, as illustrated in FIGS. 1-4 of the accompanying drawings.
When a human being walks, he leans backwards and forward with each step (FIG. 1) and from side to side with each double step (FIG. 2). As he leans to the supporting side when taking a step the torso compresses and extends on the stepping side (FIG. 3); this means that, viewing the person from the front, the person's hips pivot up and down around an imaginary center line (indicated in broken lines in FIG. 3). This is termed `up and down` movement in the present specification. In addition, as shown in FIG. 4, the person's hips move with his legs, but his torso and arms swing in the opposite direction, with the body pivoting at the waist. In FIG. 4, a line through the shoulders is indicated by line S--S and a line through the hips is indicated by line H--H. As shown in FIG. 4, there is a considerable relative rotation between the shoulders (line S--S) and the hips (line H--H) with each step. This is termed `twisting` movement in the present specification.
Also, when a human being bends or steps up, his back extends; the further the person leans forwards, the longer his back becomes. This extension of the back is in a curved plane, following the natural curve of the back.
Because of the above described movements, a hip belt which is rigidly secured to the pack, and which therefore moves with the pack, is very uncomfortable for the wearer, because the hip belt is constantly rubbing against the wearer due to the relative movements of different parts of the wearer's body when walking. The hip belt cannot be loosened to prevent this rubbing, because the belt must fit snugly to transmit load to the wearer's pelvic girdle and relieve the load on his back. FIG. 5 of the accompanying drawings shows, in diagrammatic form, the effect of a person wearing a pack with a rigidly-secured hip-belt bending forwards; the back extension raises the pack and lifts the hip-belt from the hips, applying uncomfortable pressure across the front of the lower abdomen (arrow P).
Known designs of hip-belt either are secured rigidly to the pack or allow very little relative movement, in one plane only, between the pack and the hip-belt.